Former President Lee Myung-bak speaks to reporters before entering the Seoul Central District Prosecutors' Office in southern Seoul, Wednesday. / Joint Press Corps.

By Jung Min-ho

Former President Lee Myung-bak is being investigated at the Seoul Central District Prosecutors' Office over allegations of corruption.

Lee, 76, who is accused of playing a central role in many illegal activities during his five-year term.

After arriving there at around 9:25 a.m., Lee said he was sorry for bringing concerns.

"I stand here with a saddened heart and feel sorry for bringing concerns to the nation at the time when it faces major challenges," Lee said. "I want to spare words at this moment and I hope I will be the last former president to be brought to the prosecution."

Lee, who was in office from 2009-2013, is suspected of receiving "black budgets" from the National Intelligence Service and misappropriating the money. One former aide, Kim Baek-joon, has already been indicted on this charge. But prosecutors suspect Kim only delivered the money to his boss, Lee.

Lee is also accused of using DAS, an auto parts company, to collect and manage slush funds.

He has denied any wrongdoing, calling the investigation politically motivated.

He is the country's fifth president prosecutors will have questioned over corruption allegations.

Last month, prosecutors sought a 30-year prison term for former President Park Geun-hye, his successor. Park was ousted last year amid an influence-peddling scandal and is standing trial on charges of bribery, abuse of power and coercion.